Process of recovering ammonia and hydrocyanic acid.



PATENTED DEG. 5, 1905.

I W. FELD. I PROCESS OF RBOOVERING AMMONIA AND HYDROQYANIG ACID.

APPLICATION FILED JAN. 30. 1904.

WITNESSES 11mm STATES PATENT OFFICE.

WALTHER FELD, HONNINGEN-ON-THE-RHINE, GERMANY. PROCESS OF RELCO VER I NGAMMONIA AND HY DROGYANIC ACID.

Specification of Letters Patent.

Patented Dec. 5, 1905 Application filed January 30,1904. Serial No.191,372.

To all whom it may concern:

Be it known that LWALTHER FELD, a subject of the King of Prussia, GermanEmperor, residing at Honningen-on-the Rhine, Province of the Rhine,Kingdom of Prussia, German Empire, have invented a new and usefulprocess for the simultaneous recovery of ammonia and hydrocyanic acidfrom gasescontaining the same and the partial regeneration of the agentsemployed in the recovery.

In order that my invention may be understood and practiced by thoseskilled inthe art, I give the following specification thereof.

The invention relates to processes for the recovery of ammonia andhydrocyanic acid from gases containing the same, and has for its objectthe simultaneous recovery of both the gases mentioned. a

Hitherto processes for the treatment of ammonia and the 'other for therecovery of the rest of the ammonia. Furthermore, by the influence offree ammonia and'of basic ammonia compounds'(carbonate, sulfid, andcyanid) part of the cyanogen has been lost by the formation ofsulfocyanid, especially in the treating of'gases which containcomparatively much oxygen besides sulfureted hydrogen,

such as gases from coking-ovens and blastfurnaces.

The process, according to my present invention, has for its object toenable practically the whole quantity of ammonia and of hydrocyanic acidpresent in the gases tobe recovered in one operation and to avold theformatlon of sulfocyanids neutralizing the whole of the free ammonia andthe basic ammonia compounds and forming neutral ammonia saltsimmediately the gas comes into contact with the absorbing means and byabsorbing the whole of the hydrocyanic acid in the same solution,forming an iron-cyanogen compound. For this purpose the gases aretreated with a liquid containing an iron compound or compounds,(especially ferrous compounds,)

together with salts, as hereinafter explained, in such proportions thatfor each six molecules of cyanogen in the gas at least one atom of ironis used and that for each molecule of ammonia in the gas there is usedat least one salt and the basic compound of the metal of 1 the saltused. These salts are the acid and neutral salts of non-basic reactionof the alkalies, earth alkalies and magnesia, and of those metallicearths and metals which are decomposed by basic ammonia compounds,(ammonium hydroxid, ammonium carbonate, sulfid, and cyanid.) To absorbthe Whole of the cyanogen in the gas, it is necessary for the gas tocontain at least four molecular proportions of ammonia to every sixmolecular proportions of hydrocyanic acid if a basic iron compound, suchas iron hydroxid or iron carbonate, be'us ed, together with the salt;according to the following equation:

If a neutral iron compound be used, there must be in the gas to everysix molecular proportions of cyanogen at least six molecular proportionsof ammonia, according to the following equation: 9

(2) T figEeOyH-4NH,O1+(NHQ580,.

If there be less ammonia in the gas, ammonia must be added to it, or anequivalent of another basic material may be introduced with the saltsolution. I may add the required additional ammonia to the gas beforewashing it, or I may add the said ammonia to the solution used forwashing. If there be more ammonia than the equivalent of the hydrocyanicacid, the ammonia will be absorbed by decomposition of the salt used,according to the equation:

and if a salt of an alkali or earth alkali or of magnesia be usedthe-excess of ammonia will be absorbed by the simultaneous reaction ofthe salt and the carbonic acid in the gas upon the ammonia, according tothe following equa- I IIO then-carbonicracid gas or gases containingcarlution:

bonic acid may be added to the gas, or the salt solution may be treatedwith carbonic acid or a bicarbonate may be added to the salt so- In anycase besides the iron compound, equivalent to the hydrocyanic acid, somuch of the other salt must be used that the whole of the ammonia isabsorbed to form a neutral salt. An excess of absorbing means, the ironcompound, the salt, and of carbonic acid is not objectionable. Thesolution after having been used for washing the gases contains in theform of a neutral salt all the ammonia of the gas treated and also itcontains iron -cyanogen compounds, and (according to the nature of thesalt used) the hydrates or carbonates, or, if sulfureted hydrogen waspresent in the gas, the sulfids of the metal of the salt.

It is preferable to treat the gases with the absorbing solution beforethe gases are cooled below 30 centrigrade.

The solution can be used warm without interfering with the completenessof the absorption. According to the concentration of the solution theinsoluble compounds are from time to time filtered off, if necessary,after precipitating the ferrocyanid and adding an iron compound. Thusthecyanid is obtained as Prussian blue or as an insoluble alkakiearthalkalior magnesia ferrocyanid or double ferrocyanid, such ascalcium-iron ferrocyanid, (CaFe2Cy6,) and the Suitable salts for use inconjunction with an.

iron compound in carrying out this invention are acid and neutral saltsof a non-basic character, such as the haloid salts, thev sulfates, thesulfites, the phosphates, nitrates, and similar salts of an alkali,earth alkali, magnesia, the metallic earths, or of the metals, alone ormixed together. 1

For further explaining my invention more clearly I give the followingspecific example, in which a mixture of calcium chlorid and ferroussulfate is used as the absorbing means for washing the gas. The calciumchlorid used in the process may be recovered from the waste liquors.

Example: Let it be presumed that coal-gas of normal composition is to betreated containing in .one hundred cubic meters about two thousand gramsof carbon dioxid, fifteen hundred grams of sulfureted hydrogen, three.hundred and forty grams of ammonia,"and one hundred and fifty-six gramsof .hydrocyanic acid. Such coal-gas shows a ratio of six' molecularproportions of hydrocyanic acid to twenty molecular proportions ofammonia and forty-five molecular proportions of carbon dioxid. Forabsorbing the amount of ammoniapresent in such gas ten molecularproportions of calcium chlorid are required, bearing in mind that it ispreferable to use aslight excess ofcalihm chlorid. For

In order to recover the whole of the ammonia and of the hydrocyanic acidpresent in one hundred cubic meters of the gas mentioned, at least twohundred and eighty grams of ferrous sulfate (FeSOiJHQO) and from onethousand to thirteen hundred grams of calcium chlorid are required.Having ascertained the amount of compounds present in the gas, Icalculate according to the last foregoing equations the amount ofchemicals necessary for washing the gas, and then I take this calculatedquantity of the chemicalsaccording to the present example two hundredand eighty grams of ferrous sulfate (FeSOiTI-IQO) and from onethousandto thirteen hundred grams of calcium chloridand I dissolve the saidchemicals in water. I have found it suitable to prepare a solution ofsuch a concentration that after having finished the washing process Iobtain a solution containing about five per cent. of ammonia, (in theform of ammonium chlorid.) For this purpose 1 use about seven liters ofwater for the above-mentioned quantity of absorbing substances. I mayuse a larger or smaller quantity of water for dissolving the salts; buttheir quantity is not diminished. The skilled operator will determinethe degree of concentration most suitable for his particular purpose.

In the accompanying drawing I have illustrated an apparatus suitable forcarrying out my invention.

The solution of the absorbing salts is charged into a suitable vessel 6,which may be of cylindrical form and closed by a lid 0. The gas to betreated is introduced into the vessel and caused to flow through theabsorbing solution through the pipe a, the gas afterward passing out bymeans of pipe 0Z, through which it may be conducted to a suitablecollecting-chamber or gas-holder or directly to the place where it isintended to be used, or if the gases are not intended to be used theymay be allowed to escape from the pipe (15. After the washing processhas been finished there remains in the vessel 6 a solution of sludgehaving a faint odor of coal-gas. Said solution is practically free from'sulfureted hydrogen, which is not soluble in the saidsolution, and saidsolution contains about four per cent. calcium ferrocyanid (CazFeGyt) orcalc um-ammonium ferrocyanid, fifteen per.

cent. ammonium chlorid, (NI-1401,) ten per cent. calcium'carbonate,(CaCOs,) and 1.5 per cent. calcium sulfate, (CaSOiJ the two last:

named substances being mostly undissolved; The sludge or solution in thewasher or vessel is then heated to-distiloff ammonia and to regeneratethe salt used forits absorptionfi This may be carried out in the vessel6 by introducing steam and leading away the gases.- formed by the actionof the heating process through the pipe 0?, or, if desired, I maydischarge the solution and sludge from'theves-i sel 0) and carry out theheating process in an-' other suitable vessel, or instead of introducingsteam to the vessel Z) I may heat the mixture therein directly by aflame or in any other suitable way. The skilled operator will 7 employthe method for this part ofthe proc-; ess best suited to the specialconditions under; Before or during the heat-i ing process I may addcalcium hydroxid in which 3 heworks.

the quantity as indicated by the following equation: v

(8) "ttttti@2ac0,+2ONH,+3Co,+1m,

An excess of calcium hydroxid over the amount indicated in the aboveequation is not ob ectionable, but is not necessary.- From the mass thusfreed from ammonia 1 may separate the cyanogen compounds if the solutionbe of suitable concentration (which I- may obtain by evaporating thewater or'by repeatedly using the mass for washing the gas) by adding asuitable iron compound for instance, a ferric or ferrous compoundbyation after having added the iron compounds necessary for absorbing thehydrocyanic acid in the gas to be treated. -I have found that the warmerthe liquor containing the absorbing substances is during the washingoperation Y the purer will be the solution of ammonia salt and theferrocyanid resulting from the p rocess.

, I'have found that a temperature of from 30 to 60 centigrade is verysuitable for the purposes of my invention, ammonium sulfid beingdissociated at above 3O centigrade, and therefore with the liquid of 30centigrade and higher no After the ammonia has been disammonium sulfid,and therefore no polysulfid and no sulfocyanid, can be formed. Itherefore prefer .to'wash the gas before it has been cooled below 30centigrade in order to avoid the formation of sulfocyanid compounds inthe gas before it comes into contact with my washing solution. Therecovery of the am-. monia and cyanogen can, however, be effected evenif the gas be washed with the mixture'of iron compounds and the saltsaccording to my invention at a temperature below 30- centigrade.

Having set forth and described my invention and the manner of practicingthe same,

what I claim, and desire to secure by Letters Patentjis I 1. A processfor simultaneously recovering ammonia and cyanogen from gases'containing the same, which consists in treating said gases with aliquid containing an iron compound and a salt in the proportionssubstantially as specified, said iron compound being of a character toreact with the cyanogen cyanogen compound, and said-salt being of a ofreacting with ammonia in the presence of ammonia compound, whereby thehydrocyanic acid. and the ammonia are absorbed by the iron compound andthe salt respectively.

2. A process for simultaneously recovering ammonia and cyanogen fromgases containing the same, which consists in treating said gases with aliquid containing a non-acid iron compound and a salt in the proportionssubpresent in the gas and form therewith an iron --hydrocyanic acid toform therewith a neutral non-basic character and having the propertystantially as specified, said non-acid iron compound being of acharacter to react with the cyanogen present in the gas and formtherewith an iron-cyanogen compound, and said salt'being of anon-basiccharacter and having the property of reacting with ammonia in thepresence of hydrocyanic acid to form therewith a neutral ammoniacompound,

whereby the hydrocyanic -acid-and the amthe saltrespectively.

-I I O monia are-absorbed by the iron compound and 3. A process forsimultaneously recovering ammonia and cyanogen'from gases containing thesame, which consists in treating said gases with a liquid contammg anon-ac1d ferrous compound and a salt in the proportions substantially asspecified, said iron compound being of a character to reactwi'th thecyanogen present in the gas-and form therewith an iron cyanogencompound, and said salt being of a non-basic character and having'theproperty of reacting with ammonia in the presence of hydrocyanic acid toform therewith a neutral ammonia compound, whereby the hydrocyanic acidand the ammonia are absorbed by the iron compound and the saltrespectively.

. 4. A process for simultaneously recoyering ammonia and cyanogen fromgases containing 3 the same, which consists in treating said gases Witha liquid containing an iron compound and a salt in the proportionssubstantially as specified, and at a temperature above centigrade orthereabout, said iron compound being of a character to react with thehydrocyanic acid present in the gas and form therewith an iron-cyanogencompound, and said salt being of a non-basic character and having theproperty of reacting with ammonia in the presence of hydrocyanic acid toform therewith a neutral ammonia compound, whereby the hydrocyanic acidand the ammonia are absorbed by the iron compound and the saltrespectively.

5. A process for simultaneously recovering ammonia'and cyanogen fromgases containing .the same, which consists in treating said gases with aliquid containing an iron compound and a salt in the proportionssubstantially as specified, said iron compound being of a charactertoreact with the hydrocyanic acid present in the gas and form therewith anironcyanogen compound, and said salt of a nonbasic character which iscapable of reaction with basic ammonia compounds and forming therewith aneutral ammonia compound in the presence of cyanogen, whereby the wholeof the cyanogen present in the case is absorbed by the iron compound andthe whole of the ammonia is absorbed by the said salt.

6. A process for simultaneously recovering ammonia and cyanogen fromgases containing the same, which consists in treating said gases with aliquid containing a ferrous compound and a salt in the proportionssubstantially as specified, said iron compound being of a character toreact with the cyanogen present in the gas and'form therewith aniron-cyanogen compound, and said salt of a non-basic character andhaving the property of reacting with the ammonia in the presence ofcyanogen and forming with the ammonia a neutral ammonia compound,treating the sludge to distil ofi" and recover the ammonia, thentreating the residue thus freed from ammonia with a precipitant toprecipitate the ironcyanogen compound formed.

In witness whereof I have hereunto signed my name, this 16th day ofJanuary, 1904, in the presence of two subscribing witnesses.

WALTHER FELD.

Witnesses:

WOLDEMAR HAUPT, HENRY HASPER.

